Thermal insulation and method of making the same



Oct. 1, 1935. E, HURRELL 2,016,039

THERMAL INSULATION AND METHOD OF MAKING THE SAME Filed.April 7, 1932INVENTOR Elmer LS1 Harrell.

QM m ATTORNEY Patented Oct. 1, 1935 PATENT OFFICE THERMAL INSULATION ANDMETHOD OF MAKING THE SAME Elmer S. Hurrell, Redwood City, Calif.,assignor to Johns-Manville Corporation, New York, N. Y., a corporationof New York Application April 7, 1932, Serial No. 603,745

. 4 Claims. (Cl. 154-28) This invention relates to thermal insulationand method of making the same, and particularly to a thermal insulatingarticle with an integral waterproof jacket. The invention pertainsespecially to an article comprising a relatively thick layer of thermalinsulating material, a thin sheet of fabric secured to a surface of thelayer of thermal insulating material, and a sheet of waterproof materialsecured to the outer surface of the said fabric.

A preferred embodiment of the invention is magnesia pipe covering to theouter surface of which is adhesively secured a thin sheet of wool feltwith a sheet of asphalt-impregnated asbestos paper adhesively secured tothe outer surface of the wool felt.

An object of the invention is to provide a weatherproof or waterproofinsulating article. Another object is to provide a thermal insulatingarticle with a waterproof covering adhered to the material comprisingthe inner portion of the insulating article in such manner as tominimize the entrance of water between the outer waterproof cover andthe material comprising the inner portion of the insulator. Anotherobject is to provide an interlining material adapted to be adhesivelysecured to a firm surface of a layer of thermal insulating material onone side and to be adhesively secured on the other side to awaterproofing sheet or layer. Other objects and advantages will appearfrom the detailed descrip-- nesium carbonate and 15 of (asbestos fibers.It is conventional to make 85% magnesia by a process comprising mixing,in wet condition, basic magnesium carbonate with asbestos fibers andpumping the resulting slurry to molds with filtering sides. Thus wateris removed from the slurry, by means of the filtering sides of the mold,and the solid content of the slurry is shaped approximately to the formdesired. A common form into which the 85% magnesia is shaped is oneadapted for use in covering pipes, such as steam pipes that are to beinsulated. For this purpose the 85% magnesia is usually applied in theform of semitubes, which semitubes are fitted together around the steampipe in a manner known to those skilled in the art. I

The importance of keeping insulation dry is well, understood and nmerous attempts have turesas 85% magnesia will withstand.

been made to protect 85% magnesia insulation from the'entrance of water.Thus, there have stapling at intervals or binding against the in- 10sulation by means of wrapping with wire. It will i be observed thatneither of these expedients prevents theentrance of moisture, as in theform of moist air, between the waterproofing layer and the inwardlydisposed thermal insulating material. 15 There has been difficultyheretofore in adhering a waterproof covering continuously to the surfaceof the so-called 85% magnesia. Thus, adhesives that penetrateasphalt-saturated rag felt or roofing paper do not secure a goodanchorage 20 in the magnesia. Other types of pipe covering that havebeen described comprise a material adapted to resist moderatetemperatures, such as asbestos paper or 85% magnesia, with a relativelythick surrounding layer of organic fiber, such as wool felt or eelgrass. It will be understood that organic fibers will not withstand ashigh tempera- A preferred embodiment of the present invention isillustrated in the drawing in which 30 Fig. 1 shows a perspective viewof a sectionof tubular pipe covering partly opened for insertion arounda pipe to be insulated.

Fig. 2 shows a perspective view of the same insulation after applicationaround a section of pipe, 35 cementing the flap in place over the joint,and placing a securing band around the outside of the section of pipecovering.

Fig. 3 shows an enlarged end view of a portion of the thermal insulatingarticle of the type 49 shown in Figs. 1 and 2.

In the various figures, like reference characters indicate like parts.

. The insulating article comprises a relatively thick layer ofinsulating material I, which is 5 suitably 85% magnesia, a relativelythin sheet of wool felt 2 adhesively secured to the firm outer surfaceof the insulating material, and, on the outside, waterproofasphalt-impregnated asbestos paper 3 which is adhesively secured to theouter 5 surface of the wool felt. The insulating material i is dividedinto two semitubular halves, as illustrated. Each of these two halveshas an edge 6 and an edge I which, when the insulation has beeninstalled around a pipe, abut with the cor- 55 responding edges of theother half to give two longitudinal joints or zones of contact. Thesheets ,of wool felt 2 and waterproofed asbestos paper 3 are adhesivelysecured over the outer edge of the zone of contact-of the edges 1 andprovide a structure which may be opened like a hinge. The wool felt andasbestos paper, in the article as shipped to the user, do not cover thejoint between the edges 6. The fact that this joint or zone of contactis not covered permits opening of the tubular pipe covering andapplication around the pipe ID that is to be insulated. The outer layerof waterproof paper has a free portion 4 adapted to extend, as a flap,over the joint between the edges 8 and to be adhesively secured oversuch joint or zone of contact after the insulation has been installedaround the pipe Ill. The installed pipe covering may be encircled by theband 5.

In the enlarged view of a fragment shown in Fig. 3 there may be seen, inaddition to the parts already described, the adhesive material 8, whichsecures the wool felt 2 to the thick layer of insulating material I andalso the adhesive material 9, which secures the outer layers, consistingof waterproof asbestos paper, to the outer surface of the wool felt, orto an outer surface of a lower layer of the waterproof asbestos paperwhen more than one layer of such asbestos paper is used. It should beunderstood that the thickness of these layers of adhesive is exaggeratedin Fig. 3, for cleamess of illustration. As a matter of fact theadhesive constitutes a very thin layer, except for that part of theadhesive which penetrates one or more of the two materials that areadhesively secured to each other.

The thickness of the layers of materials used may be varied withinlimits. However, it is preferredto have the main body of insulating ma-.terlal, such as magnesia, represent most of the total thickness of theinsulating articles Thus, for a layer of 85% magnesia that isthreefourths of an inch thick, there may be used a backing sheet of woolfelt, as illustrated at 2, that is thin, say approximately one-fiftiethof an inch thick. The wool felt interlining is covered, in turn, withthin asphalt paper sheeting, such as sheeting of about the samethickness as the wool felt. It is suitable to use a plurality, as, forexample, three layers of such sheeting on the outside of a single layerof the wool felt. In general, the wool felt may well be not more than atenth and suitably approximately one-thirtieth of the thickness of thelayer of 85% magnesia.

This use of a relatively thin layer only of felted' organic fibersbehind a relatively thick layer of insulating material such as 85%magnesia is quite desirable. It provides that most of the volume of theinsulation shall be taken by 85% magnesia, for example, which is notonly relatively inexpensive and effective as an insulating material butalso resistant to moderate temperatures such as those obtained by steamlines even when carrying steam at temperatures up to about 500 degreesFahrenheit. The thick layer of magnesia protects from decomposition theorganic fibers of the wool felt which, in the structures of the presentinvention, are spaced near the outside of the insulating article andwell away from the object that is insulated.

0n the other hand, even a thin layer of a flexible and water-permeablefabric, such as wool felt, is adequate to permit adhesively securing itby means of an aqueous cementing material to the firm outer surface ofthe 85% magnesia insulation and also to permit adhesively securing anouter sheet of waterproofing material, such'as asphalt-impregnatedasbestos paper, to the flexible and water-permeable fabric. In fact thewater-permeable felt, as well as the outer water- 5 proof material,should be so thin as to be flexible and to yield readily, along thehinge-like joint at the edges 1 of the pipe covering, without causingbreakage of the magnesia when the tubular section is opened. For thesame reason, the kind 10 and quantity of adhesives 8 and 8 used shouldbe such as to ensure yieldability of the covering felts.

The cement or adhesive used in -the layers 8 and 3 is suitably anaqueous solution of water 15 glass. Such an aqueous adhesive penetratessatisfactorily the water-permeable felt.

In making the improved article containing 85% magnesia as the thicklayer of insulating material, there is first prepared, in conventionalmango ner, semitubular sections of 85% magnesia pipe covering. Thesesections are sized or painted on the outer surface with a solution of 30B. silicate of soda solution, partly in'order to prevent excessiveabsorption of silicate in the subsequent application of the layer ofwool felt. Two sections are then put together so that the edges 8 and Iabut to form longitudinal joints. The wool felt is then adhered, bymeans of 40 36. silicate of soda solution, to the sized sin-face of the85% 30 magnesia. So applied, this wool felt readily absorbs the silicatecement and adheres to the previously sized section of insulationmaterial, the

cement thus being caused not only to adhere thoroughly to thewool feltbut also integrally unite 35 with the water-soluble sizing materialimpregnated into the magnesia. The wool felt and magnesia are thendried, to remove the water added with the adhesive. As the outer,waterproof material, there is used impregnated asbestos paper, suitablyone containing '6 pounds of asbestos paper stock, ,dry weight, andaproximately 3 pounds of asphalt impregnating material for each 108square feet. Before application, this impregnated asbestos felt or paperis warmed to approximately deg. F., to soften or increase the pliabilityof the paper that is otherwise relatively stiff, that is, stiffer thanthe wool felt used as the interliner. The warmed asphalt and asbestospaper is then treated with 40 B. silicate of soda solution and wrappedto a thickness of 3-4 plies around the tube consisting of 85% magnesiaand the outwardly adhered layer of wool felt. An additional two inchesor so of width of the asphalt and asbestos paper is allowed for a lap.This lap is not applied with silicate of soda during fabrication but isleft free to be cemented down later.

-The fully wrapped section is now placed in a dryer forthe purpose-ofremoving the water applied in the silicate solution. As the articlecools to atmospheric temperature, subsequent to the drying operation,the asphalt in the paper is hardened and the paper is therebystifl'ened. The waterproof wrapping and the interlining sheet of woolfelt is then cut lengthwise, on one'side only, at the joint between theedges 6 of the two pieces of semitubular 85% magnesia. This cuttingallows the section to be opened up, with one zone of contact of theedges of the two semitubes covered with felt and sheeting actingsimilarly to a hinge, for application around a pipe. After suchapplication the lap mentioned above is adhesively secured over the otherzone of contact of the edges of the semitubes. In this manner there ismade a watertight joint, as well as an insulating 75 article that has anintegrally united waterproof covering adhesively secured to theprincipal body of insulating material in such manner as to minimize thepenetrability by water and the entrance of moisture between thewaterproof covering and the insulating material. While such a productwould not withstand immersion or soaking of an end in liquid water, theproduct is weatherproof to a substantial degree and represents animportant advance over an insulating article comprising 85% magnesiapipe covering with a surrounding waterproof covering stapled to themagnesia or tied thereto with wire,'in such manner as to leave spacesbetween the covering and the surface of the 85% magnesia. It should beadded that the band 5, placed around my'improved pipe covering, afterthe lap 4 is cemented into position, is not absolutely necessary butdoes decrease the chance of tearing or loosening the flap 4.

When sections of pipe covering are installed around a pipe to beinsulated, the adjacent sections of pipe covering form both longitudinaland. end joints. The closing of the longitudinal joint by means of aflap has been described. The end joint may be made weatherproof also, byadhesively securing a strip of waterproof paper, such asasphalt-impregnated asbestos paper, around and over the end joint.

While the invention has been illustrated as applied to theweatherproofing of 85% magnesia insulation, the invention is usefulwith-other types of insulating products. Thus there may be used othertypes of non-laminated insulating material as a substitute for the 85%magnesia. For example, the interlining felt as a means of adhesivelysecuring a waterproof exterior jacket to an inner body of insulatingmaterial may be used in connection with the insulating compositionmadefrom lime, diatomaceous earth, and asbestos, as described in UnitedStates Patent 1,045,933 to 'Belknap, or in connection with an insulatormade from magnesium bicarbonate, diatomaceousearth, and asbestos, asdescribed in United States Patent 1,279,975 to Boeck and Jordan.

For the purpose of insulating high pressure steam lines the inner bodyof insulating material should have insulating efficiency and resistanceto shrinkage at elevated temperatures at least equal to that of 85%magnesia, in order to prevent shrinkage or decomposition of theinsulating material itself as well as of the material, such as feltedorganic fibers, outside the insulation.

Since the purpose of the wool felt is to provide a relatively softmembrane adapted to receive the cementing material and also to yieldsufficiently to give good contact, on one side,with the firm surface ofthe inner body of insulating material and, on the other, with theoutwardly applied waterproofing layers, other relatively soft,water-permeable materials may be substituted for the wool felt. Thusthere may be used a thin sheet of unimpregnated asbestos paper,preferably made in as soft a form as is consistent with adequatestrength for the purpose of holding the outer layer of waterprooforegnated'with asphalt, another waterproof fabric adhesively secured tothe flexible and waterpermeable interlining fabric. Thus there may beused rag felt or paper or wool cloth that is thoroughly impregnated witha waterproofing material, such as asphalt, tar, or a wax. However, theuse of impregnated asbestos paper is preferred because of the knowndesirable properties of asbestos in thermal insulating compositions.

Insulating articles of other shapes than pipe covering may be made. Thusa rectangular block of 85% magnesia may be, adhesively secured to oneside of a sheet of wool felt, and an outer waterproof sheeting, such asasphalt-impregnated roofing paper, then adhesively secured to the otherside of the wool felt. The surface of the insulating block to which thewool felt is adhered is that which during use is to be remote from theobject insulated.

Since many variations from the illustrative details given may be madewithout departing from the scope of the invention, it is intended thatvariations within the spirit of the invention should be included withinthe scope of the claims.

What I claim is:

1. A thermal insulating article comprising a shaped firm mass of 85%magnesia, water-soluble sizing material impregnated thereinto, a thinwater-permeable fabric disposed around the sized magnesia, an adhesivesecuring the fabric to the magnesia, being integral with the said sizingmaterial and being thoroughly adhered to the fabric, .and a waterproofsheet material continuously adhered over substantially the entire outersurface of the said fabric.

2. A, tubular thermal insulating article adapted for use as covering forsteam pipes, said insulating article comprising a layer of 85% magnesia,a

sheet of felted organic fibers adhesively secured to the outer surfaceof the layer of magnesia, and a sheet of waterproof asbestos paperadhesively secured to the outer surface of the sheet of organic fibers,the thickness of the sheet of felted organic fibers being not more thana tenth of that of the layer of 85% magnesia.

3. A tubular thermal insulating article of minimized penetrability bywater, said insulating article comprising a tube of 85% magnesia or thelike, divided into two semitubes with edges thereof abutting in twolongitudinal zones of contact, a thin sheet of felted organic fibersadhesively secured to substantially the entire outer surface of the tubeof- 85% magnesia, a waterproof sheet adhesively secured to substantiallythe entire outer surface of the sheet of felted organic fibers, the saidsheets covering one of the zones of contact of the edges of the twosemitubes, and a portion of the waterproof sheet adapted to extend, as afiap, and to be adhesively secured over the other zone of contact.

4. In making an insulating article comprising 85% magnesia and awaterproof covering interally un.ted thereto, the process which includespreparing sections of 85% magnesia insulation, coating the outer surfacethereof with a. sizing material of .the type of a solution ofwaterglass, adhesively securing thereto a flexible fabric of fibers thatis permeable to the said solution, providing a waterproof sheet of thetype of asphaltimpregnated roofing, softening the said waterproof sheet,adhering the softened sheet to the said flexible fabric, and thenincreasing the stiffness of the said waterproof sheet.

ELMER S. HURRELL..

